I'm just experimenting, what works, what doesn't work ect. I haven't needed the trap so far, but since I'm taking the rescue class soon, I figured I'd try to address all elephants, before hand, the tech shorts seem like a good buy.
Part of Rescue class, indeed a big part of it, is to try and see what works and what doesn't. Don't buy equipment specifically for the course, learn to adapt the the solutions to work with the type of equipment you dive in. Sometimes it can identify minor issues with some's kit configuration, and we work through that (offer alternatives so they can see what solution) may work better.
PS: I also dive a TransPac (and Transplate) and find no issues with a crotch strap - I have mine set so that on land the waist belt is pulled slightly down - but underwater you don't notice this. I also use a very soft crotch strap webbing